The Molecular Mechanism And Fluroescence Detection Of Heat-Tolerant Differentiation Of Ageratina Adenophora

Ageratina adenophora has strong reproductive ability,fast growth rate and wide ecological adaptability,which decide its strong invasive ability.It infects farmland, orchards,wasteland,mountains,grasslands,harms to agriculture,forestry,animal husbandry,destroys ecosystems,leads to serious local biodiversity loss,seriously impacts on local production and life.Moreover,it has rich genetic diversity and has occurred an ecological adaptive change to various habitate and different climate conditions.The ecological adaptation differentiation to hot temperature is one of the most important performance,which will help Ageratina adenophora invade wide region.However,its heat tolerance differentiation mechanism is not clear.Heat shock protein gene related to heat-tolerance was cloned and its function expression was analyzed,and chlorophyⅡfluorescence parameters tested in different populations were compared in order to elucidate the molecular mechanism and photosynthetic mechanism of different heat tolerance in different populations of Ageratina adenophora.HSP17.7 and HSP17.6 were cloned from heat-shocked leaves of Croflon weed(Ageratina adenophora) using RT-PCR and RACE-PCR technques with degenerate primers designed from conserved motifs found in a number of plant cytosolic clsssⅠsHSP genes,named HSP17.7 and HSP17.6.Their accession numbers are EF105483 and EF520125 in the GeneBank.The Semi-quantitive RT-PCR results revealed that the gene HSP17.7 can be detected at normal temperature but was significantly different between different tissues.The transcription of HSP17.7 in leaves and stems were higher than those in roots.Besides,the expression of HSP17.7 was significantly increased under heat treatment and chilling treatment.Heated shock eight hours,HSP17.7 expression amounted to the top.Recombinant HSP17.7 was overexpressed in Escherichia coli to study its possible function under heat and chilling stress.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of cell lysates suggested that HSP17.7 was expressed in Escherichia coli.The growth of wild type and transformed cells was similar at 37℃.Upon transfer from 37℃to 50℃,a temperature known to cause cell autolysis,those cells that accumulated HSP17.7 exhibited improved viability compared with the control cultures. Similar result was observed under chilling treatment at 4℃as well.These results indicated that sHSP involved in Crofton weed responseinig to heat and chilling stress.Photosynthesis stability at different temperature,especially high temperature,were studied in different heat-tolerant populations of Crofton weed(YuXi,HuangGuoShu and DaLi) by measuring polyphasic chlorophyll fluorescence transients and electrolyte leakage under different temperature treatments.The temperature of Fo rising threshold was shifted 2℃and 7℃lower in DaLi(38℃) than in the HuangGuoShu(40℃) and the YuXi(45℃) respectively.With increasing temperature the rate of decline in fluorescence parameters of Dali were larger than that HuangGuoShu and YuXi.The trend of electrolyte leakage with temperature change was also consistent with the above fluorescence parameter results.All results indicated that the main part of heat damage to PhotosystemⅡwas oxygen-evolving activities(OEC).The different thermostability of PSⅡstructure and function in different populations may be the one of reasons that leads to different heat-resistance.